1. Field of the Invention
This invention generally relates to distributed unit communications and, more particularly, to a system and method for synchronizing the collection of data in a time division multiple access (TDMA) network.
2. Description of the Related Art
Data acquisition systems may be required to synchronously gather data from physically separated data generator units (DGU), each with its own internal clock, while consuming a minimal amount of power to maximize battery life and operational time. Each DGU is typically assigned a timeslot in a TDMA (time division multiple access) system so all DGUs can operate on a single physical layer resource (such as a single radio frequency).
One example of a DGU is an IMU (inertial measurement unit) attached to a user's body segments (such as the leg thigh and shank) for the purpose of measuring the RoM (range of motion) of the intervening joint (such as the knee). The IMUs must synchronously gather data so that the orientations of the body segments are measured at the same time. Measuring at different times could cause an error in calculating the relative orientation of one body segment compared to the other if both body segments are moving relative to the Earth.
Since each DGU has its own internal clock, their time bases may drift relative to each other, causing a loss of synchronization. Timing signals must be sent between the various DGUs to maintain clock synchronization. To maximize the system's battery life, timing signals should be kept to a minimum, as transmission and reception generally consume power and thus reduce system battery life.
TDMA systems typically use a single master time base generator, to which slave devices synchronize their clocks. The master device typically uses more power than the slave devices, since it needs to communicate with all slaves to maintain the synchronized communication link, while each individual slave only needs to communicate with the master, and not with the other slaves. There may be other resources, such as storage memory, which the master device consumes more quickly than slave devices.
Conventional TDMA data generator systems do not dynamically select their master device from the group of devices. They require a dedicated master device. This has the undesirable consequences of either requiring a special, separate master device, or causing the DGU acting as the master device to consume its battery more quickly than other devices and thus reduce overall system operational time.
It would be advantageous if TDMA data acquisition systems could dynamically select their master to optimize overall system operational time, and maintain system synchronization during the transition of the Link Master role from one DGU to another. Such a feature would distribute resource consumption more equally amongst the group of data generators.